Re: WARNING in batadv_iv_send_outstanding_bat_ogm_packet

[Anant Thazhemadam]

On 16/09/20 10:25 am, Dmitry Vyukov wrote:
> On Tue, Sep 15, 2020 at 8:34 PM Anant Thazhemadam
> <anant.thazhemadam@xxxxxxxxx> wrote:
>> On Monday, October 14, 2019 at 2:25:08 AM UTC+5:30 syzbot wrote:
>>> Hello,
>>>
>>> syzbot found the following crash on:
>>>
>>> HEAD commit: da940012 Merge tag 'char-misc-5.4-rc3' of git://git.kernel..
>>> git tree: upstream
>>> console output: https://syzkaller.appspot.com/x/log.txt?x=13ffd808e00000
>>> kernel config: https://syzkaller.appspot.com/x/.config?x=2d2fd92a28d3e50
>>> dashboard link: https://syzkaller.appspot.com/bug?extid=c0b807de416427ff3dd1
>>> compiler: clang version 9.0.0 (/home/glider/llvm/clang
>>> 80fee25776c2fb61e74c1ecb1a523375c2500b69)
>>> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=141ffd77600000
>>> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11edd580e00000
>>>
>>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
>>> Reported-by: syzbot+c0b807...@xxxxxxxxxxxxxxxxxxxxxxxxx
>>>
>>> ------------[ cut here ]------------
>>> WARNING: CPU: 1 PID: 30 at net/batman-adv/bat_iv_ogm.c:382
>>> batadv_iv_ogm_emit net/batman-adv/bat_iv_ogm.c:382 [inline]
>>> WARNING: CPU: 1 PID: 30 at net/batman-adv/bat_iv_ogm.c:382
>>> batadv_iv_send_outstanding_bat_ogm_packet+0x6b4/0x770
>>> net/batman-adv/bat_iv_ogm.c:1663
>>> Kernel panic - not syncing: panic_on_warn set ...
>>> CPU: 1 PID: 30 Comm: kworker/u4:2 Not tainted 5.4.0-rc2+ #0
>>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
>>> Google 01/01/2011
>>> Workqueue: bat_events batadv_iv_send_outstanding_bat_ogm_packet
>>> Call Trace:
>>> __dump_stack lib/dump_stack.c:77 [inline]
>>> dump_stack+0x1d8/0x2f8 lib/dump_stack.c:113
>>> panic+0x264/0x7a9 kernel/panic.c:221
>>> __warn+0x20e/0x210 kernel/panic.c:582
>>> report_bug+0x1b6/0x2f0 lib/bug.c:195
>>> fixup_bug arch/x86/kernel/traps.c:179 [inline]
>>> do_error_trap+0xd7/0x440 arch/x86/kernel/traps.c:272
>>> do_invalid_op+0x36/0x40 arch/x86/kernel/traps.c:291
>>> invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1028
>>> RIP: 0010:batadv_iv_ogm_emit net/batman-adv/bat_iv_ogm.c:382 [inline]
>>> RIP: 0010:batadv_iv_send_outstanding_bat_ogm_packet+0x6b4/0x770
>>> net/batman-adv/bat_iv_ogm.c:1663
>>> Code: 66 05 00 eb 05 e8 9c 48 23 fa 48 83 c4 68 5b 41 5c 41 5d 41 5e 41 5f
>>> 5d c3 e8 88 48 23 fa 0f 0b e9 34 ff ff ff e8 7c 48 23 fa <0f> 0b e9 28 ff
>>> ff ff 89 d9 80 e1 07 80 c1 03 38 c1 0f 8c c1 f9 ff
>>> RSP: 0018:ffff8880a9abfc48 EFLAGS: 00010293
>>> RAX: ffffffff874fe8a4 RBX: ffff888094160870 RCX: ffff8880a9ab2080
>>> RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000002
>>> RBP: ffff8880a9abfcd8 R08: ffffffff874fe28e R09: ffffed10123e6969
>>> R10: ffffed10123e6969 R11: 0000000000000000 R12: ffff888091f34000
>>> R13: dffffc0000000000 R14: ffff8880a80c5000 R15: ffff8880a4481400
>>> process_one_work+0x7ef/0x10e0 kernel/workqueue.c:2269
>>> worker_thread+0xc01/0x1630 kernel/workqueue.c:2415
>>> kthread+0x332/0x350 kernel/kthread.c:255
>>> ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
>>> Kernel Offset: disabled
>>> Rebooting in 86400 seconds..
>>>
>>>
>>> ---
>>> This bug is generated by a bot. It may contain errors.
>>> See https://goo.gl/tpsmEJ for more information about syzbot.
>>> syzbot engineers can be reached at syzk...@xxxxxxxxxxxxxxxx.
>>>
>>> syzbot will keep track of this bug report. See:
>>> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>>> syzbot can test patches for this bug, for details see:
>>> https://goo.gl/tpsmEJ#testing-patches
>>
>> For this bug, syzbot does not seem to be able to build the kernel anymore.
>> Can bugs like these be considered and closed as invalid?
>>
>> Thanks,
>> Anant
> Hi Anant,
>
> +syzkaler, lkml (nobody is generally reading syzkaller-bugs).
>
> What do you mean by "not able to build a kernel for this bug"?
> Building a kernel is not related to a particular bug. It's the same
> for all bugs...

Hi,

I thought this might be a query that's better suited for the syzkaller groups,
and hence posted it on there.

I wanted to check if this bug was still present and relevant, so I tried to check
by sending a syz test request for the upstream kernel (the dashboard shows
that the error was found in the upstream kernel).

However, I was notified later that the build/boot had failed.
Feel free to correct me if I'm wrong, but I doubt that the reason build/boot
had failed, was because of the bug itself (the error report is visible on the
bug's dashboard page itself).

I wanted to know what was the typical protocol in cases like this. Would this be
a valid reason enough to close the bug as invalid? Or is there something else
that can be done, to indicate that the upstream kernel doesn't even build/boot
for this bug to be tested anymore?
If nothing else, how else can I try and get syzbot to test if this bug still exists or
not?

Thanks,
Anant